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FAN5332A High Efficiency, High Current Serial LED Driver and OLED Supply with 30V Integrated Switch
August 2005
FAN5332A High Efficiency, High Current Serial LED Driver and OLED Supply with 30V Integrated Switch
Features
1.5MHz Switching Frequency Low Noise Adjustable Output Voltage Up to 1.5A Peak Switch Current 1.5W Output Power Capability Low Shutdown Current: <1A Cycle-by-Cycle Current Limit Over-Voltage Protection Fixed -Frequency PWM Operation Soft Start Internal Compensation Thermal Shutdown 5-lead SOT-23 Package
Description
The FAN5332A is an LED driver that features fixed frequency mode operation and an integrated FET switch. The device's high output power makes it suitable to drive flash LEDs in serial connections. This device is designed to operate at high switching frequencies in order to minimize switching noise measured at the battery terminal of hand-held communications equipment. Quiescent current in both normal and shutdown mode is designed to be minimal in order to extend battery life. Normal or shutdown mode can be selected by a logic level shutdown circuitry. The low ON-resistance of the internal N-channel switch ensures high efficiency and low power dissipation. A cycle-by-cycle current limit circuit keeps the peak current of the switch below a typical value of 1.5A. The FAN5332A is available in a 5-lead SOT23 package.
Applications
Cell Phones PDAs Handheld Equipment Display Bias LED Bias Flash LED
Typical Application
VIN CIN 10F 5 1 R1 CF 82pF 2.7V to 5.5V L 6.8H BAT54 COUT 2.2F VOUT
FAN5332A
VIN
SW
FB
3
R2 ON OFF 4 SHDN GND 2
Figure 1. Typical Application Diagram
(c)2004 Fairchild Semiconductor Corporation
1
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FAN5332A Rev. 1.0.1
FAN5332A High Efficiency, High Current Serial LED Driver and OLED Supply with 30V Integrated Switch
Pin Assignment
Top View SW GND FB VIN SHDN
5-Lead SOT-23
Figure 2. Pin Assignment
Pin Description
Pin No.
1 2 3 4 5
Pin Name
SW GND FB SHDN VIN Switching Node. Analog and Power Ground.
Pin Description
Feedback Pin. Feedback node that connects to an external voltage divider. Shutdown Control Pin. Logic HIGH enables, logic LOW disables the device. Input Voltage Pin.
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FAN5332A High Efficiency, High Current Serial LED Driver and OLED Supply with 30V Integrated Switch
Absolute Maximum Ratings (Note1)
Parameter
VIN to GND FB, SHDN to GND SW to GND Lead Soldering Temperature (10 seconds) Junction Temperature Storage Temperature Thermal Resistance (JA) (Note 2) Electrostatic Discharge Protection (ESD) Level (Note 3) HBM CDM 2 1 -55 -0.3 -0.3
Min
Max
6.0 VIN + 0.3 35 300 150 150 200
Unit
V V V C C C C/W kV
Recommended Operating Conditions
Parameter
Input Voltage Output Voltage Operating Ambient Temperature Output Capacitance (Note 4)
Min
2.7 12 -40 1.6
Typ
Max
5.5 30
Unit
V V C F
25
85
Notes: 1. Stresses above those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Absolute maximum ratings apply individually only, not in combination. 2. Junction to ambient thermal resistance, JA, is a strong function of PCB material, board thickness, thickness and number of copper planes, number of via used, diameter of via used, available copper surface, and attached heat sink characteristics. 3. Using EIA/JESD22A114B (Human Body Model) and EIA/JESD22C101-A (Charge Device Model). 4. This load capacitance value is required for the loop stability. Tolerance, temperature variation, and voltage dependency of the capacitance must be considered. Typically a 2.2F ceramic capacitor is required to achieve specified value at VOUT = 30V.
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FAN5332A High Efficiency, High Current Serial LED Driver and OLED Supply with 30V Integrated Switch
Electrical Characteristics
Unless otherwise noted, VIN = 3.6V, No external load,TA = -40C to +85C, Typical values are at TA = 25C, Test Circuit, Figure 3. Parameter
Output Voltage Accuracy Switch Current Limit Load Current Capability Switch On-resistance Quiescent Current OFF Mode Current Shutdown Threshold Shutdown Pin Bias Current Feedback Voltage Feedback Pin Bias Current Line Regulation Load Regulation Switching Frequency Maximum Duty Cycle Enable Delay Power on Delay Switch Leakage Current VIN = 2.7V, IOUT = 50mA, VOUT = 20.7V VIN = 2.7V, IOUT = 50mA, VOUT = 20.7V No Switching, VIN = 5.5V 3.2V < VIN < 5.5V, VOUT = 20.7V, TA= 25C 0mA < ILoad < 75mA, VOUT = 20.7V 1.2 87 VIN = 3.2V VOUT > 18.5V, VIN 2.7V VOUT > 19.7V, VIN 3.2V, TON < 0.4Sec. VIN = 5V VIN = 3.6V VSHDN = 3.6V, No Switching VSHDN = 3.6V, Switching, VOUT = 20.7V VSHDN = 0V Device ON Device OFF VSHDN = 0V or VSHDN = 5.5V TA= 25C 1.205 1 1.230 1 0.5 0.8 1.5 93 1.5 1.5 5 5 1 1.8 1.5 0.5 100 1.255 100 1.5
Conditions
Min.
-3 1.1 50 75
Typ.
1.5
Max.
+3
Units
% A mA mA
0.6 0.7 0.7 4.5 0.1 3
mA mA A V V nA V nA % % MHz % mS mS A
Test Circuit
VIN CIN 10F 5 V 1 R1 CF 82pF 2.7V to 5.5V L 6.8H BAT54 COUT 2.2F VOUT
SW
160K
FAN5332A
IN
FB
3
R2 ON OFF 4 SHDN GND 2
10K
Figure 3. Test Circuit
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FAN5332A High Efficiency, High Current Serial LED Driver and OLED Supply with 30V Integrated Switch
Typical Performance Characteristics
TA = 25C, CIN = 10F, COUT = 2.2F, L = 6.8H, unless otherwise noted.
Line Regulation
22
R OUT = 275
Full Load Efficiency
90
R OUT = 275
Output Voltage (V)
21
80
20
Efficiency (%)
TA = 25C TA = 85C
70
TA = 25C
T A = 85C
19
TA = -40C
60
TA = -40C
18 2.5
3.0
3.5
4.0
4.5
5.0
5.5
50 2.5
3.0
3.5
4.0
4.5
5.0
5.5
Battery Voltage (V)
Battery Voltage (V)
No Load Battery Current vs. Battery Voltage
6
TA = 25C
Light Load Efficiency
85
I Load = 20mA
5
Battery Current (mA)
80
4
TA = 85C
Efficiency (%)
75
I Load = 10mA
3 2 1 0 2.5
TA = -40C
70
65
3.0
3.5
4.0
4.5
5.0
5.5
60 2.5
3.0
3.5
4.0
4.5
5.0
5.5
Battery Voltage (V)
Battery Voltage (V)
Load Transient Response
V IN = 3.6V VOUT = 20.7V ROUT = 275
Start-Up Response
Output Voltage (5V/ div ) ENABLE Inductor Voltage Current (5V/d iv) (50 0mA/di v)
VIN = 3.6V
Output Voltage (500m V/d iv)
Load Regulation
Load Current Step
75 mA 0mA
Time (100s/div )
Tim e (500s/div)
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FAN5332A High Efficiency, High Current Serial LED Driver and OLED Supply with 30V Integrated Switch
Block Diagram
SHDN 4
Shutdown Circuitry
VIN 5
SW 1
FB
+ Over
Voltage
- Comp 1.15 x VREF
Thermal Shutdown
R FB 3 +
Error Amp
+ Comp -
R R S
Q
Driver
n
Ramp Generator Oscillator
Current Limit Comparator -
+
+ Amp Reference Soft-Start
0.03W
2 GND
Figure 4. Block Diagram
Circuit Description
The FAN5332A is a pulse-width modulated (PWM) current-mode boost converter. The FAN5332A improves the performance of battery-powered equipment by significantly minimizing the spectral distribution of noise at the input caused by the switching action of the regulator. To facilitate effective noise filtering, the switching frequency was chosen to be high, 1.6MHz. An internal soft start circuitry minimizes in-rush currents. The timing of the soft start circuit was chosen to reach 95% of the nominal output voltage within maximum 5mS following an enable command when VIN = 2.7V, VOUT = 20.7V, ILOAD = 35mA and COUT (EFFECTIVE) =2.2F. The device architecture is that of a current mode controller with an internal sense resistor connected in series with the N-channel switch. The voltage at the feedback pin tracks the output voltage at the cathode of the external Schottky diode (shown in the test circuit). The error amplifier amplifies the difference between the feedback voltage and the internal bandgap reference. The amplified error voltage serves as a reference voltage to the PWM comparator. The inverting input of the PWM comparator consists of the sum of two components: the amplified control signal received from the 30m current sense resistor and the ramp generator voltage derived from the oscillator. The oscillator sets the latch, and the latch turns on the FET switch. Under normal operating conditions, the PWM comparator resets the latch and turns off the FET, thus terminating the pulse. Since the comparator input contains information about the output voltage and the control loop is arranged to form a negative feedback loop, the value of the peak inductor current will be adjusted to maintain regulation. Every time the latch is reset, the FET is turned off and the current flow through the switch is terminated. The latch can be
reset by other events as well. Over-current condition is monitored by the current limit comparator which resets the latch and turns off the switch instantaneously within each clock cycle. Over-voltage condition is detected by a fast comparator limiting the duty cycle in a similar manner to over-current monitoring described above. Dimming may be accomplished by PWM modulating the SHDN input at a frequency around 100Hz.
Over-Voltage Protection
The voltage on the feedback pin is sensed by an OVP Comparator. When the feedback voltage is 15% higher than the nominal voltage, the OVP Comparator stops switching of the power transistor, thus preventing the output voltage from going higher.
Applications Information
Setting the Output Voltage
The internal reference (VREF) is 1.23V (Typical). The output voltage is divided by a resistor divider, R1 and R2 to the FB pin. The output voltage is given by R1 V OUT = V REF 1 + ------ R 2 According to this equation, and assuming desired output voltage of 20.7V, good choices for the feedback resistors are, R1=160k and R2=10k.
Inductor Selection
The inductor parameters directly related to device performances are saturation current and dc resistance. The FAN5332A operates with a typical inductor value of 6.8H. The lower the dc resistance, the higher the efficiency. Usually a trade-off between
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FAN5332A High Efficiency, High Current Serial LED Driver and OLED Supply with 30V Integrated Switch
inductor size, cost and overall efficiency is needed to make the optimum choice. The inductor saturation current should be rated around 1.5A, which is the threshold of the internal current limit circuit. This limit is reached only during the start-up and with heavy load condition; when this event occurs the converter can shift over in discontinuous conduction mode due to the automatic turn-off of the switching transistor, resulting in higher ripple and reduced efficiency. Some recommended inductors are suggested in the table below:
ered in applications such as a flash LED driver. An operation time of 0.4Sec. at maximum load, followed by a 3.6Sec. OFF time ensures stable operation even in the worst case, provided that the IC heat dissipation is optimized to lower the junction to ambient thermal resistance. The external passive components and the layout of the PCB play an important role in reaching the highest efficiency of the boost converter. For best results, the data sheet recommendations regarding external components and PCB layout should be followed closely.
PCB Layout Recommendations
The inherently high peak currents and switching frequency of power supplies require careful PCB layout design. Therefore, use wide traces for high current paths and place the input capacitor, the inductor, and the output capacitor as close as possible to the integrated circuit terminals. The resistor divider that sets the output voltage should be routed away from the inductor to avoid RF coupling. A two layer PCB with the bottom layer as ground plane connected to the pin 2 of the IC is recommended. This ground plane acts as an electromagnetic shield to reduce EMI and parasitic coupling between components.
Inductor Value Vendor
6.8H 6.8H 6.8H TDK MURATA COOPER
Part Number
SLF7028T6R8M1R3 LQ566C6R8M04 SD414-6R8
Comment
Low Profile High Efficiency Small Size
Table 1: Recommended Inductors Capacitors Selection
For best performance, low ESR input and output capacitors are required. Ceramic capacitors of CIN = 10F and COUT = 2.2F placed as close to the IC pins, are recommended for the lower input and output ripple. The output capacitor voltage rating should be according to the VOUT setting. Some capacitors are suggested in the table below.
Capacitor Value
10F 2.2F
Vendor
Murata Murata
Part Number
GRM31CR70J106KA01B GRM32RR71E225KC01B
Table 2: Recommended Capacitors
A feed forward capacitor CF, is required for stability. The recommended value (R1 x CF) is around 13S.
Figure 5. Recommended PCB Layout
Diode Selection
The external diode used for rectification is usually a Schottky diode. Its average forward current and reverse voltage maximum ratings should exceed the load current and the voltage at the output of the converter respectively. A barrier Schottky diode such as BAT54 is preferred, due to its lower reverse current over the temperature range. Care should be taken to avoid any short circuit of VOUT to GND, even with the IC disabled, since the diode can be instantly damaged by the excessive current.
Thermal Shutdown
When the die temperature exceeds 150C, a reset occurs and will remain in effect until the die cools to 130C, at that time the circuit will be allowed to restart.
Heavy Load Limitations
In heavy load applications (POUT >1.5W) the power dissipated in steady state at high ambient temperature can increase the die temperature to the point where the thermal shutdown kicks in. To prevent this, a limited time operation should be consid-
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FAN5332A High Efficiency, High Current Serial LED Driver and OLED Supply with 30V Integrated Switch
Mechanical Dimensions
5-Lead SOT-23Package
B e c E H e1 D A A1 L
Symbol Min
A A1 B c D E e e1 H L .087 .004 0 .035 .000 .008 .003 .106 .059
Inches Max
.057 .006 .020 .010 .122 .071 .037 BSC .075 BSC .126 .024 10
Millimeters Min
.90 .00 .20 .08 2.70 1.50 .95 BSC 1.90 BSC 2.20 .10 0 3.20 .60 10
Notes
Max
1.45 .15 .50 .25 3.10 1.80
Ordering Information
Product Number
FAN5332A
Package Type
5-Lead SOT23
Order Code
FAN5332ASX
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FAN5332A High Efficiency, High Current Serial LED Driver and OLED Supply with 30V Integrated Switch
TRADEMARKS
The following are registered and unregistered trademarks Fairchild Semiconductor owns or is authorized to use and is not intended to be an exhaustive list of all such trademarks.
ACExTM FAST ActiveArrayTM FASTrTM BottomlessTM FPSTM Build it NowTM FRFETTM CoolFETTM GlobalOptoisolatorTM CROSSVOLTTM GTOTM DOMETM HiSeCTM EcoSPARKTM I2CTM E2CMOSTM i-LoTM EnSignaTM ImpliedDisconnectTM FACTTM IntelliMAXTM FACT Quiet SeriesTM Across the board. Around the world.TM The Power Franchise Programmable Active DroopTM
DISCLAIMER
ISOPLANARTM LittleFETTM MICROCOUPLERTM MicroFETTM MicroPakTM MICROWIRETM MSXTM MSXProTM OCXTM OCXProTM OPTOLOGIC OPTOPLANARTM PACMANTM POPTM Power247TM PowerEdgeTM
PowerSaverTM PowerTrench QFET QSTM QT OptoelectronicsTM Quiet SeriesTM RapidConfigureTM RapidConnectTM SerDesTM SILENT SWITCHER SMART STARTTM SPMTM StealthTM SuperFETTM SuperSOTTM-3 SuperSOTTM-6
SuperSOTTM-8 SyncFETTM TinyLogic TINYOPTOTM TruTranslationTM UHCTM UltraFET UniFETTM VCXTM WireTM
FAIRCHILD SEMICONDUCTOR RESERVES THE RIGHT TO MAKE CHANGES WITHOUT FURTHER NOTICE TO ANY PRODUCTS HEREIN TO IMPROVE RELIABILITY, FUNCTION OR DESIGN. FAIRCHILD DOES NOT ASSUME ANY LIABILITY ARISING OUT OF THE APPLICATION OR USE OF ANY PRODUCT OR CIRCUIT DESCRIBED HEREIN; NEITHER DOES IT CONVEY ANY LICENSE UNDER ITS PATENT RIGHTS, NOR THE RIGHTS OF OTHERS. LIFE SUPPORT POLICY FAIRCHILD'S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF FAIRCHILD SEMICONDUCTOR CORPORATION. As used herein: 2. A critical component is any component of a life 1. Life support devices or systems are devices or support device or system whose failure to perform can systems which, (a) are intended for surgical implant into be reasonably expected to cause the failure of the life the body, or (b) support or sustain life, or (c) whose support device or system, or to affect its safety or failure to perform when properly used in accordance with instructions for use provided in the labeling, can be effectiveness. reasonably expected to result in significant injury to the user. PRODUCT STATUS DEFINITIONS Definition of Terms Datasheet Identification Advance Information Product Status Formative or In Design Definition This datasheet contains the design specifications for product development. Specifications may change in any manner without notice. This datasheet contains preliminary data, and supplementary data will be published at a later date. Fairchild Semiconductor reserves the right to make changes at any time without notice in order to improve design. This datasheet contains final specifications. Fairchild Semiconductor reserves the right to make changes at any time without notice in order to improve design.
Preliminary
First Production
No Identification Needed
Full Production
Obsolete
Not In Production
This datasheet contains specifications on a product that has been discontinued by Fairchild semiconductor. The datasheet is printed for reference information only.
Rev. I16
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